Sometimes I wonder if there is anything that hasn't been linked to autism.
Environmental factors are important for all kind of health issues, from cancer to fertility to the common cough andmental health issues. But they are globally a mess. In the western world our way of living has changed incredibly in the last century :
- Different diet (carbs/proteins/fat balance, vegetal/animal balance, etc.)
- Different food (food preparation has changed a lot due to new appliances, fashions and ways of eating, and crops/cattle are grown/raised in completely different ways)
- Pollution (atmospheric, in water, in food, etc.)
- Modern medicine (vaccines, and globally many more different drugs, much more readily available)
- Urbanization
- More generally, completely different material environment (omnious electric lighting, air conditioning, new transportation systems, etc.)
- Different social organization (for example living alone is much more common, and family structures have changed a lot)
- Different ways to work
- Different education system
- Everything computers and modern telcos changed
(- We could go on for a very long time on various sociological aspects)
I am quite convinced that most, if not all, of those have an impact on many aspects of everyone's health. But I think that in many cases that influence comes from a combination of many factors and therefore attempts to link a condition to a single cause are doomed. If there is a "formula" to understand the problem it is likely not something simple like "X causes autism" but more likeley "X, Y, the absence or Z, the presence of A or B, and either the absence of C or the presence of D, is almost guaranteed to produce an autistic individual".
To take an example that is both completely unrelated and about something easier to measure than autism and mental health, let's take male fertility. It has been known for a while that sperm quality (concentration of spermatozoids and proportion of viable spermatozoids) has been plummeting in western Europe during the last decades. In France, for example, both have fallen by about 30%. This is thought to be caused by environmental or lifestyle factors such as pollution, diet or alcool consumption. A recent study has mapped the evolution of sperm quality between 1989 and 2005 in various areas of France, and has found that indeed the evolution is completely different depending on the location. In some areas, like the south west, the fall is the strongest, whereas in brittany for example sperm quality has actually got better. The scientist are trying to draw correlations between the evolution and some specificities of each area, but they are struggling. It looks like genetics play no role, alcohol consumption is not significant at all (brittons for example are quite heavy drinkers), atmospheric pollution does not seem to matter much either (zones with very high population density do not suffer from an outstanding loss). Diet in general does not seem to matter (people from the southwest globally have a quite healthy diet). The most significant thing they have found until now is use of pesticides for agriculture, but it does not completely match the data either. That is just an exemple, but it shows that science is struggling to find the causes of even a phenomenon that is easy to characterize and to measure, where data is available, and where genetic factors have been ruled out. Autism (and most mental health issues) fits none of those criteria. So I think we should not expect a complete explanation any time soon.
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ouroboros
A bit obsessed with vocabulary, semantics and using the right words. Sorry if it is a concern. It's the way I think, I am not hair-splitting or attacking you.